Many surgical procedures utilize surgical devices secured to the bone of a patient. In some instances, a bone plate may be utilized that spans and secures together one or more bones or pieces thereof. In other instances, a screw or other fastener may be fastened to a bone without another device, such as a screw used to secure a transplanted tendon.
In many of these procedures, it is preferred to create a pilot hole in the bone prior to securing the fastener in the bone. Oftentimes, this preference arises from the importance of having a fastener that is inserted to a proper depth. That is, the opposite side of the bone from the drill site will typically be abutted by soft tissues that may be harmed if the screw is too long. As an example, a fastener mounted in the pedicle portion of the human spine should not extend to a point where the fastener contacts the spinal cord itself, an event that can cause irreparable nervous system damage including paralysis.
In other examples, immediate short-term damage is not a significant issue from slight over-drilling because the tissue on the opposite side will heal quickly. Over-drilling through a metacarpal may simply result in damage to the fat layer within the finger. However, if a screw is used that is too long, it may protrude and be tactilely felt by the patient, or it may pierce the skin itself. In addition, the screw may prevent soft tissues moving over the bone surface, such as tendons, ligaments, or muscles.
During drilling, the surgeon is typically capable of recognizing the resistance on the drill in order to determine when the drill has penetrated through the bone. Because the simple act of drilling does not provide an exact measurement of the depth of the bone itself, a depth gauge is commonly employed for directly measuring the depth of the hole from the top, drilling side to the bottom, opposite side.
Currently, many designs are known and utilized for measuring the depth of a hole or bore in a portion of a bone. Generally speaking, these designs utilize a central probe member having a barb at a distal end, and a sleeve or channel member. The probe member is inserted into the pilot hole while the surgeon attempts to find the surface with the barb. More specifically, the probe member is inserted to a depth greater than the depth of the pilot hole so that the barb is beyond the opposite side, at which point the surgeon finds the surface by hooking the barb to the opposite side.
The probe member is received in the sleeve or channel member and may reciprocate relative thereto. The channel member has graduated markings along a portion of its length, typically in inches and/or millimeters. A marker is laterally secured to the probe member such that, as the probe member shifts relative to the channel member, the marker indicates the relative shift between the probe member and the channel member. Accordingly, once the probe member has been secured to the opposite side of the bone, the channel member is shifted relative to the probe member and toward the bone until the channel member abuts the surface of the bone. The depth gauge is then read by examining graduated markings indicated by the probe member marker.
A number of problems are experienced with this depth gauge. As an initial point, the components are typically made with surgical-grade stainless steel, and the graduated markings are embossed therein. Therefore, the brightness of the operating room lights on the highly reflective surface can make the markings difficult to read. The markings are commonly in small increments, such as millimeters, and surgeons often have trouble differentiating between the markings, or noting partial increments. Reading these gauges, then, often requires carefully holding the depth gauge as the reading is taken, and a surgeon's effort to closely examine the reading may result in a loss of securement or purchase of the barb on the bone, thus necessitating a re-measurement and a loss of time.
Proper reading of the markings requires a surgeon's eyes to be properly aligned with the markings. That is, a proper view of the measurement requires the surgeon to view the gauge from a lateral point of view so that the view of the probe marker aligned with the graduated markings is proper not distorted by the surgeon's elevated, standing perspective. Therefore, it is often necessary for the surgeon to bend over while using these gauges to view an accurate reading. If the depth gauge is tilted in order to make the reading, the sleeve will shift relative to the probe, thus making the measurement inaccurate and possibly causing the barb to become unsecured, as discussed above.
In addition, removing of the depth gauge often causes the measurement to be lost. As the bone is essentially clamped, by light pressure, between the distal end of the channel member and the distal barb of the probe member, it is often necessary to retract the channel member from the bone surface in order to extract the probe from the pilot hole.
Additionally, if such retraction were not necessary, it is still difficult to extract the barb of the probe member without altering the measurement reading. Because the pilot hole has a relatively small diameter, and the probe member is relatively deflectable, a small amount of manipulation is required to remove the probe member. When this manipulation is through cancellous bone, the barb may become snagged while being extracted. These issues are compounded by the fact that the surgical procedure often requires multiple screws, and surgeons prefer to move quickly by taking their measurements, selecting their screws, and securing the screws in the pilot holes, each in rapid succession. Clearly, it would be difficult and unwise to rely on a surgeon's ability to remove the depth gauge without altering the measurement provided in order to make a selection of fastener length.
Accordingly, there has been a need for an improved depth gauge for surgical procedures.